Derelict (i.e., lost or abandoned) commercial fishing gear, including nets and traps, can present safety, nuisance, and environmental impacts in estuarine waters. Blue crabs and various fish species that are entrapped and die in derelict traps can act as an attractant to other crabs, resulting in a self-baiting effect. Derelict fishing gear damages sensitive habitat and continues to capture both target and by-catch species, leading to reduced fitness and significant acute and delayed mortalities. Animals captured in derelict traps can experience starvation, cannibalism, infection, disease, and prolonged exposure to poor water quality (i.e., low dissolved oxygen).
The number of derelict crab traps in the nation's estuaries is unknown. Typically, traps can become derelict for a number of reasons, e.g., buoy lines can be severed by vessel propellers or break due to age, buoy materials can fail, storms can roll the traps pulling the buoy below the surface, and traps can be vandalized or abandoned. In a pilot study in Virginia, the density of derelict pots in a specific crab fishing sector was determined to be about one pot per 28 square meters (587 ghost pots/16,400 m2) (Havens, K. J., et al. “The effects of derelict blue crab traps on marine organisms in the lower York River, Virginia”, North American Journal of Fisheries Management (2008), 28, pp. 1194-1200).
It has been suggested that 250,000 derelict crab traps are added to the Gulf of Mexico annually, based on an estimated 25% loss/abandonment rate and an annual total number of traps fished commercially of approximately 1 million. The Gulf States Marine Fisheries Commission has estimated blue crab derelict fishery losses of as high as 4 to 10 million crabs a year in Louisiana (Guillory, V., et al., Proceedings: Blue Crab Mortality Symposium, Gulf State Marine Fisheries Commission (2001) Ocean Springs, Miss., pp. 28-41).
The effect of derelict blue crab traps on diamondback terrapins (Malaclemys terrapin) and commercially important finfish is significant, and various states and regions have enacted measures to reduce the ecological and economic impacts of derelict traps. For example, the state of Florida enacted regulations (CH 46-45, F.A.C., effective Jan. 1, 1995) establishing degradability requirements for blue crab traps. Traps are considered to have a legal degradable panel if panels are secured to each other using degradable materials such as jute twine or a corrodible hook. Unfortunately, many blue crab traps having such degradable panels or connections continue to trap and retain fish and crabs long after the degradable part has degraded. The same issues can occur with lobster traps.
It is desirable for crab traps to have cull rings, also called escape rings or escape hatches, to allow small and juvenile crabs to escape the trap. Typically, such cull rings have an inside diameter of at least 2.25 inches. For example, the state of Florida enacted regulations (CH 46-45, F.A.C., effective Jun. 1, 1994) requiring all blue crab traps to have at least 3 unobstructed escape rings installed, each with a minimum inside diameter of 2.375 inches. Lobster traps are also are required to have escape hatches of varying sizes, with the cull ring size dependent on the jurisdiction.
There remains a need for an improved degradable crab trap that, within a period of months after it becomes derelict, loses its ability to trap fish and crabs. To reduce the economic burden on fishermen, it would be advantageous if a degradable element could be inexpensively incorporated into existing traps for lobsters or crabs, thereby providing the desired degradability in derelict traps without requiring the purchase of expensive new traps.